The presently described technology generally relates to a device for detecting a shaft fracture in a gas turbine, in particular on a gas turbine aircraft engine. Furthermore, the present technology also relates to a gas turbine.
Gas turbines designed for aircraft engines typically have at least one compressor, at least one combustion chamber and at least one turbine. Aircraft engines known in the art typically have three compressors positioned upstream from the combustion chamber and three turbines positioned downstream from the combustion chamber. The three compressors of the aircraft engines include a low-pressure compressor, a medium pressure compressor and a high-pressure compressor. The three turbines of the engine include a high-pressure turbine, a medium pressure turbine and a low-pressure turbine. As it is known to those of ordinary skill in the art, rotors of the high pressure compressor and high pressure turbine, of the medium pressure compressor and medium pressure turbine and of the low pressure compressor and low pressure turbine are each connected by a shaft, such that the three shafts are arranged concentrically about each other, such that the shafts are encapsulated one inside the other.
By this arrangement described above, if there is a fracture in the shaft connecting the medium pressure compressor and the medium pressure turbine, then the medium pressure compressor can no longer draw any work or power from the medium pressure turbine, thus establishing an excessive rotational speed on the medium pressure turbine. Such wheel spinning of the medium pressure turbine must be prevented because it can damage the entire aircraft engine.
Thus, for safety reasons, a shaft fracture in a gas turbine must be reliably detectable so that the supply of fuel to the combustion chamber may be interrupted when a shaft fracture occurs. Such detection of a shaft fracture poses problems, particularly if the gas turbine has three concentric and therefore encapsulated shafts, one inside the other, as described above. In particular, the detection of a shaft fracture of the middle shaft connecting the medium pressure turbine to the medium pressure compressor is extremely difficult, and poses even more problems. Similar problems also occur with stationary gas turbines.
DE 10 2004 026 366 A1 describes a device for detecting a shaft fracture in a gas turbine wherein an operating element is arranged radially on the inside of the shaft, between the last rotor-side moving blade ring (as seen in the direction of flow) of a first turbine, and a first stator-side guide vane ring (as seen in the direction of flow) of a second turbine. The operating element cooperates with a transmission element, which extends in the radial direction through the first stator-side guide vane ring (as seen in the direction of flow) of the second turbine. In the case of a shaft fracture, the last rotor-side moving blade ring (as seen in the direction of flow) of the first turbine acts on the operating element, and the impact on the operating element is transmitted via the transmission element to a switch element, which is arranged radially on the outside of the housing of the gas turbine.